The present invention relates to the apparatus of a rotary regenerative air preheater. More particularly, the invention relates to axial seal plates of air preheaters.
A rotary regenerative air preheater transfers sensible heat from the flue gas leaving a boiler to the entering combustion air through regenerative heat transfer surface in a rotor which turns continuously through the gas and air streams. The rotor, which is packed with the heat transfer surface, is divided into compartments by a number of radially extending plates referred to as diaphragms. These compartments are adapted to hold modular baskets in which the heat transfer surface is contained.
The air preheater is divided into a flue gas side or sector and one or more combustion air sides or sectors by sector plates. In a typical installed rotary regenerative heat exchanger, flexible radial seals mounted on the top and bottom edges of the diaphragms are in close proximity to these sector plates and minimize leakage of gas and air between sectors. Similarly, flexible axial seals mounted on the outboard edge of the diaphragms are in close proximity to axial seal plate assemblies mounted on the inner surface of the housing and minimize leakage therebetween.
Conventional axial seal plate assemblies include numerous component parts. The axial seal plate generally includes a pair of side plates which are each mounted to the side edges of a curved sealing plate by long seam weld. Multiple support ribs are mounted to the radially outer surface of the axial seal plate to provide pressure stiffening. The support ribs are usually burned to a radius and are welded to the sealing plate. The long length of the weld joining the side plates to the sealing plate leads to various weld distortions, which effect the close tolerances required for the axial seal plate.
The axial seal plate seal surface it set at its proper position through the use of access doors on each side of the seal plate, which allow access for measuring the critical sealing gaps on each side of the axial seal plate assembly.
Briefly stated, the invention in a preferred form is an axial seal plate for an air preheater having a single, unitary structure including a sealing portion disposed intermediate first and second end portions extending orthogonally from the sealing portion. The axial seal plate does not including any welds for joining the end portions to the sealing portion.
Preferably, the axial seal plate also has first and second transition portions disposed between the sealing portion and the first and second end portions, respectively. Each transition portion extends at an angle of 45xc2x0 from the sealing portion and the respective end portion extends at an angle of 45xc2x0 from the transition portion.
The axial seal plate also includes multiple pressure stiffening bars mounted to the sealing portion. Preferably, at least one tab mounts each of the pressure stiffening bars to the sealing portion. The inner edge of each tab is welded to the outer surface of the sealing portion and the outer edge portion of each tab is welded to the pressure stiffening bar to mount the pressure stiffening bars to the seal plate.
It is an object of the invention to provide an axial seal plate which requires less structural parts and eliminates the need for access doors.
It is also an object of the invention to provide an axial seal plate which requires less welding during construction.
It is further an object of the invention to provide an axial seal plate which requires no machining of the seal surface.
Other objects and advantages of the invention will become apparent from the drawings and specification.